Strategy On CFOs Compensation For Multipoint-to-Multipoint Cooperative OFDMA Systems

As cooperative OFDMA systems are considered as a good method to improvecoverage, cell-edge throughput, and ensure the high quality of service requirements,they become a hot research topic for the next generation of mobile communication. Inmultipoint-to-multiuser (MtM) cooperative OFDMA systems, one user equipment (UE)may receive signals with different carrier frequency offsets (CFOs) from different basestations (BSs) at the same time slots and carriers. It is impossible for BSs or UEs tocompensate for the CFOs respectively. Based on the existing frequency compensationproblems，the paper provides pre-and post-compensation strategy used the maximumtolerant technology to solve it. The major contributions of this paper are listed asfollows.Firstly, introducing the cooperative OFDMA systems with related key technology,the paper discusses the systems with imperfect synchronization in time and frequencyaccording to the system model and theory analysis.Then, it researches on frequency requirement of the systems to obtain that each linkcan tolerate the maximal CFO error normalized value which is the constraint conditionby using the theory and simulation analysis.Thirdly, under the environment of CFOs in multipoint-to-point and point-to-multipoint cooperative systems, the paper gives the methods, which will use theestimation results to pre-compensate or post-compensate respectively and can achievewith the traditional frequency synchronization techniques. We present a joint pre-andpost-compensation with relaxed residual CFOs to compensate the CFOs in MtMcooperative systems. The simulation results show that the proposed strategy caneliminate the CFOs of each links effectively.The research outcomes show that the proposed strategy provides a very valuableway to eliminate CFOs in MtM cooperative systems effectively.